Some internal combustion engines include engine control systems that deactivate cylinders under specific low load operating conditions. For example, an eight cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand or DOD. Operation using all of the engine cylinders is referred to as an activated mode. A deactivated mode refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).
In the deactivated mode, there are fewer firing cylinders. As a result, there is less drive torque available to drive the vehicle driveline and accessories (e.g., alternator, coolant pump, A/C compressor). Engine efficiency, however, is increased as a result of decreased air pumping losses due to the deactivated cylinders not taking in and compressing fresh intake air.
A lifter oil manifold assembly (LOMA) is implemented to activate and deactivate select cylinders of the engine. The LOMA includes a series of lifters and solenoids associated with corresponding cylinders. The solenoids are selectively energized to enable hydraulic fluid flow to the lifters to inhibit valve lifter operation, thereby deactivating the corresponding cylinders.
A control system generates LOMA system response time estimates based on the physical properties of the solenoids, the hydraulic system, the lifters and other LOMA components. The response time estimates are implemented to inhibit mistiming errors when activating and deactivating cylinders. Traditionally, the response time estimates are based on test or timing data generated using a simulation or actual LOMA system testing. The test or timing data, however, does not account for response time variance that occurs as a result of component aging.